Various embodiments for the automatic actuation of friction clutches of transmission devices are known from practical application, which can be subdivided into housing-affixed and rotating transmission components, for instance, in regard to the manner in which energy and information are transmitted. In automatic transmissions, clutches are often actuated mechanically, wherein axial forces are typically transmitted by housing-affixed actuating devices to the rotating clutches via axially displaceable engagement and release bearings.
The disadvantage, however, is that a differential rotational speed is compensated in the region of the bearing and, depending on the axial force that is present, mechanical losses occur that reduce the efficiency of the automatic transmission.
Multi-disk clutches of automatic transmissions are typically actuated to the desired extent using hydraulic actuating devices; for this purpose, hydraulic pressure generated on the housing side is directed via a so-called rotating oil feed to the clutches having rotating hydraulic cylinders.
During operation of such transmission devices, friction occurs in the region of the sealing contact of the rotating oil supply line, which, as drag torque, reduces the efficiency of a transmission device. Moreover, the frictional heat produced in the region of the sealing contact is dissipated via a defined leakage fluid volume flow which cannot be provided without the additional pumping capacity of a hydraulic pump of the transmission device, however. The additional pumping capacity that is required reduces the efficiency of the transmission device, which is undesired.
To reduce the above-described drag torques, electromagnetic actuating devices are assigned to shift elements of transmission devices, in which case a current-carrying coil disposed on the housing side typically moves a concurrently rotating, axially displaceable coupling component to the desired extent.
Electromagnetic actuation of shift elements or clutches are characterized by excessively high current consumption, however, which may place a high load on an electrical system of a vehicle in unfavorable operating states of a vehicle drive train.
In the case of an actuation of shift elements of transmission devices characterized by low current consumption, an electric actuator that rotates concurrently with a transmission shaft, such as a magnet, an electric machine or the like, is supplied with electricity from a housing-affixed current source via slip rings.
The slip rings provided for supplying current require an excessively large amount of construction space, however, and have a short service life due to the sustained frictional load.
DE 10 2006 049 275 A1 makes known a transmission device comprising at least one shift element that can be actuated via an actuator comprising at least one electrical component. The electrical component is connected to a transmission shaft, rotates during operation at the rotational speed of the transmission shaft, and is operatively connected to further components of the transmission device via an electrical transmitting device. Electrical energy and/or data can be exchanged between the housing-affixed components of the transmission device and the at least one electrical component connected to the transmission shaft in a contactless manner via the transmitting device using induction.
However, the actuator has a structurally complex design and requires a large amount of construction space, only limited amounts of which are available in transmission devices.